This invention relates to waterbeds, and in particular to waterbed mattresses.
Waterbeds in the past have usually been made with a mattress consisting of a large, watertight bladder covered by mattress ticking, and a heavy supporting structure or frame to maintain the shape of the mattress and support the heavy weight of the water filling the bladder. A difficulty with this type of waterbed is that it cannot be moved without draining the mattress, and in view of the large quantity of water, this is time-consuming and wasteful since the water is usually not reused. A further difficulty with these waterbeds is that a leak in the bladder can cause extensive damage.
Attempts have been made to overcome the weight problem. One example of this is shown in U.S. Pat. No. 3,689,949 issued to J. D. Weinstein. Weinstein suggested the use of a base for the water bladder which was hollowed out on its top side in a shape to conform to the general shape of the human body. It was suggested that this structure would effectively reduce the weight of the water above those areas of the mattress which supported the least weight. However, this mattress was unusually bulky.
Another attempt to overcome the weight problem of conventional waterbeds is shown in U.S. Pat. No. 3,789,442 issued to S. Tobinick. This patent shows a hollowed out foamed flexible material which receives a liquid filled bladder. This bladder is also covered by a foamed flexible material. It would seem that the benefits achieved would be accompanied by a lost flotation effect.
A problem with both the Weinstein and Tobinick approaches is that these beds are very expensive to manufacture.
In order to solve the problem of leaking bladders, it has been proposed to make a separate watertight cover or envelope to enclose the main mattress bladder, so that if a leak occurs in the bladder, the water will be contained by the outer watertight cover. A problem with this solution, however, is that it must be possible to open the outer cover to insert the bladder, to fill it, and to empty it. This requires a large watertight closure which itself is prone to leakage.
It is an object of the present invention to provide a lightweight easily transportable flotation pad having a double wall to protect against leaks and which can be used to convert any ordinary bed into a waterbed.